A conventional pet separating device used in vehicles is shown in FIG. 6 and generally includes two posts 40 each have a top sucking member 43 and a bottom sucking member 44 for respectively contacting against the ceiling and the floor of the vehicle. Each post 10 includes a rod 42 and two sleeves 41 are mounted to the rod 12. Each sleeve 41 includes two extensions 411 extending radially outward and a groove 412 is defined in each extension 411 so that two transverse tubes 51 are engaged with the grooves 112. Two U-shaped parts 52 are inserted into the two open ends of the two transverse tubes 51 so as to form rounded ends.
It is experienced that the pets frequently hit the U-shaped parts 22 and the transverse tubes 51 so that the U-shaped parts 52 tend to be shaken in the transverse tubes 51 and the transverse tube 51 are loosened in the grooves 112, so that the conventional pet separating device generates a lot of noise.